This invention is directed to a wing leading edge flap and, more particularly to the mechanism for actuating the leading edge flap.
The aerodynamic design of modern aircraft wings is a compromise between many conflicting requirements, thus limiting near optimum aerodynamic performance to a small portion of their flight envelopes. Obviously, great emphasis must be placed on cruise configuration as this is the regime most frequently experienced. However, modern wings must be configured to permit variation in the airfoil geometry either in flight or on the ground to improve aerodynamic performance during other portions of the flight regime. Leading edge flaps or slats are common devices, which are made to extend from the leading edge of the wing, to improve lift coefficients during landing and takeoff operations.
Current commercial and military transport aircraft employ slat or leading edge flap systems supported by either track systems or linkages and driven by alternate schemes, including cable systems, torque tubes, or direct actuator drives, either hydraulic cylinders or ball screws. Most track systems drive the track itself, which makes for a complex and costly track system. Invariably, in either system, the motion of the drive system is oriented in a plane perpendicular to the wing chord plane. One exception to this generality is an early wing slat system disclosed in U.S. Pat. No. 2,298,264, issued to Czurles et al. However, Czurles teaches a direct drive of the track by a chain and sprocket system rather than a linkage system.
Where a linkage drive system is employed and its motion is oriented in a plane perpendicular to the wing chord plane it either makes for a complex linkage system involving several combined linkages or it requires that the linkage extends or protrudes from the wing envelope in order to achieve the necessary mechanical advantage. This is true because the wings are thin and taper from the wing root to tip.
Known flight characteristics as a result of asymmetric slat conditions make it imperative that the slat system positively lock in the extend or retract position, and every emphasis must be placed on the design to avoid a condition which permits an asymmetric slat condition to occur.
In certain aircraft, it is necessary to accommodate leading edge boundary layer control equipment, e.g. de-icing ducts, fuel tanks, or some other mechanism, in the leading edge wing structure forward of the wing front spar. It is an object of this invention to provide a slat actuating system which provides space forward of the wing front spar for other systems to pass by the slat activating mechanism. It is a further object of this invention to maintain the operating envelope of the actuating mechanism of the slat system within the conventional wing envelope. It is yet another object of this invention to provide a slat actuating mechanism which locks the slats in the fully extended position and prevents the slat from extending when the activating power is not applied to the mechanism. The final object of the invention is to provide a redundant mechanical drive characterized by light weight, easy maintenance, and improved simplicity.